1. Field of the Invention
The present invention relates to a magnetic head for use in audio, video, computer, and other applications, and more particularly to a magnetic head which is of such a structure as to keep good sliding contact with a magnetic tape for recording and reproducing signals at a high rate.
2. Description of the Prior Art
Recent magnetic recording and reproducing apparatus with rotary head drums for helical scan employ dedicated multitrack magnetic heads for recording and reproducing wide-band video signals, FM audio signals, PCM audio signals, and for erasing signals by flying erasure.
Generally, a helical-scan magnetic recording and reproducing system employs a plurality of magnetic head tips, which are all identical in shape and are made of the same material, disposed closely to each other and mounted in one window or recess in the outer circumferential surface of a rotary head drum or cylinder. The configuration of projecting portions of the head tips, and the curvature thereof in a direction transverse to the tracks are optimized for uniform contact with the magnetic tape.
Each of the magnetic head tips may be a ferrite head tip or a laminated head tip. The laminated head tip comprises a metallic magnetic body or layer sandwiched between nonmagnetic substrates, the metallic magnetic body defining a magnetic path.
To meet recent demands for long-time, high-capacity recording capabilities, thinner magnetic tapes for use in magnetic recording systems are under development. It is known, however, that the stiffness of a magnetic tape decreases in inverse proportion to the cube of the thickness thereof.
When signals are recorded on and reproduced from a standard-time recording thick magnetic tape with multitrack magnetic heads, the front configuration or contour of the head tips wears into a large radius of curvature in its transverse direction because of intimate contact with the thick magnetic tape. In general, when successive magnetic head tips are held in sliding contact with a magnetic tape, the leading head tip which is brought into initial sliding contact with the magnetic tape is subject to higher pressure than the trailing head tip which is brought into subsequent sliding contact with the magnetic tape. The higher pressure is developed because the magnetic tape flexes due to an air stream caused by the rotation of the head drum and also because the magnetic tape and the magnetic head tips move relatively to each other. Particularly, since the magnetic head tips are made of the same material, the leading head tip with respect to the direction of rotation of the head drum wears to a larger extent than the trailing head tip. Consequently, the transverse radius of curvature of the leading head tip becomes greater than that of the trailing head tip. When signals are subsequently recorded on and reproduced from a long-time recording thinner magnetic tape with the same head tips, since the thinner magnetic tape is of lower stiffness, it flexes greatly in the transverse direction, and is not sufficiently held in good contact with the leading head tip. As a result, the spacing loss is increased, and the reproduced output of the leading head tip is lower in level than the reproduced output of the trailing head tip. The reduction in the reproduced output of the leading head tip can be observed as a deterioration of the output waveform envelope.
There has heretofore been an attempt to reduce the radius of curvature of leading head tips in the transverse direction for solving the above problems. The radius of curvature greatly varies as the magnetic head tips wear, and different magnetic heads wear to different degrees as the wear progresses, resulting in different radii of curvature thereof. Therefore, the prior attempt has proven ineffective in completely eliminating the aforesaid drawbacks.